[Elecraft] center fed dipole

[Bob McGraw]

I don't understand the use of the 4:1 balun.  On 80M the feed Z of that 
antenna is more likely 25 to 50 ohms.  The 4:1 balun would present a 
impedance to the RG-213 of 6.5 to 12.5 ohms.  You would be much better 
with a 1:1 balun configuration.  Remember one is not matching the feed 
line impedance but is matching the antenna impedance.

The ideal use of a 4:1 balun is with a folded dipole antenna which 
presents a 200 to 300 ohm impedance.  Now the feed line Z is much closer 
matched and the 4:1 balun gets the Z to the coax in the 50 to 75 ohm 
range.  Much more efficient.  This of course is a single band antenna.

See https://www.dj0ip.de/balun-stuff/  for good, accurate, and reliable 
information on baluns and their usage.  Most hams have it wrong as well 
as most manufactures of antenna tuners who include a 4:1 balun.

73

Bob, K4TAX



On 10/30/2021 5:07 PM, elecraft-request at mailman.qth.net wrote:
> Message: 11
> Date: Fri, 29 Oct 2021 18:25:44 -0700 (PDT)
> From: MIKE ZANE<n6zw at comcast.net>
> To:"Elecraft at mailman.qth.net"  <Elecraft at mailman.qth.net>
> Subject: [Elecraft] center fed dipole
> Message-ID:<1705203692.528740.1635557144218 at connect.xfinity.com>
> Content-Type: text/plain; charset=UTF-8
>
> I have no problem with a 130 ft dipole fed with 25 feet of 450 ohm ladder (window) line to a 4:1 4K balun with 15 feet of RG-213 to my MFJ 989C tuner. I have run from 5w to 1 KW with it....no problems at all.  n6zw